4 14 
donum run along the side of the pancreas; 
afterwards they arrive upon the coeliac artery: 
here they receive the lymphatics' from the 
liver and gizzard, and shortly after another 
trom tire inferior part of the oesophagus. At 
the root ot the codiac artery they are joined 
by the lymphatics of the renal glands ; and 
near tire same part by the lacteals of the 
small intestines. A particular branch passes 
from the rectum, which receives some small 
vessels from- the kidneys at the root of the 
coeliac artery. The lymphatics of the infe- 
rior extremities appear to unite with those 
from the intestines. At the root of the coeliac 
artery the junction ol the lymphatics forms 
a kind of net-work, from which arise two tho- 
racic ducts, one lying on each side of the 
spine, which terminate near the angle formed 
by the jugular and subclavian veins. The 
ducts are joined by the lymphatics of the 
neck, and probably by those of the superior 
members or wings, at' the place of their en- 
trance into the jugulars. The chyle, it has 
already been observed, in all birds is like the 
lymph, transparent and colourless. 
1 lie kidneys lie in the hollow of the back- 
bone, from which the ureters pass into the 
cloaca. 1 lie testicles are placed on each 
side of the spine, and are remarkably large 
in this animal: the seminal vessels pass from 
these at lirst in a straight direction, but after- 
wards are convoluted, like the epididymis of 
the human subject. These convolutions part- 
ly supply the want of vesiculae seminales ; 
the coition however of these animals is very 
short; the vasa seminifera terminate in the 
penes, of which, in the cock, there are two. 
Ifirds in general are without prostate gland. 
From the large size of the testes this animal 
is remarkably salacious, and is capable of 
impregnating many females. Impregnation 
is effected in the following manner: The race- 
inus vitellorum of the female being analogous 
to the human ovaria, is attached by a mem- 
brane to the spine, which membrane is con- 
tinued down to the uterus. The orifice of the 
womb is averse in respect to the ovaria ; not- 
withstanding, by the force of the venereal 
orgasm, it turns round and grasps the vi- 
tellus : the substance from the racemus, in its 
passage through the duct, receives a gelati- 
nous liquor, by which, with what it after- 
wards receives in the uterus itself, the white 
of the egg is formed. The shell is lined with 
a membrane, and in the larger end there is a 
bag filled with air, for which there is no out- 
let. 
When the egg is completed, it is pushed 
out from the uterus, through an aperture 
at the side of the common cloaca. When 
the hen lays eggs that are not impregnated, 
the semen of the male has not been applied 
to the vitelli. These eggs appear to be com- 
plete, with the exception of a small black 
spot, which is that from which the rudiments 
of the chick are formed. 
General vieiv of the organs subservient to 
animal motions. 
FIRST, OF THE SKELETON. 
The bones of which the skeleton is com- 
posed are for the most part articulated, so as 
to form a whole. To this rule, however, 
there are exceptions. In birds and in qua- 
drupeds, the bones which support the tongue 
are only connected by soft parts with the' 
COMPARATIVE ANATOMY. 
general skeleton. In those quadrupeds which 
nave no clavicles, all the osseous parts of the 
anterior extremities are only attached by 
muscles; in other quadrupeds they are 
merely joined to the sternum by single cla- 
vicles, and by double ones in the class aves. 
In fishes they are connected with the ver- 
tebral column by a bony girdle. In this class 
of animals the posterior extremities are ge- 
nerally free, and simply fixed in the mlispular 
substance, while in other animals they have 
a firm connection with the rest of the skele- 
ton through the medium of the pelvis. 
There are three primary divisions of the 
skeleton ; the head, the trunk, and the ex- 
tremities. 
The first is in no instance wanting. In 
serpents, and in some fishes, the extremities 
are totally wanting. In those fishes that are 
without ventral fins (apodes Linnafi), and in 
the cetacea among the mammalia (cete Lin.), 
the posterior extremities are wanting. The 
anterior extremities only are wanting in one 
species of lizard. 
No vertebral animal has more than four 
extremities, unless we include the kind of 
wing which belongs to the flying-dragon, a 
small animal nearly similar to our lizard. 
I he trunk is formed by the vertebra;, ribs, 
and sternum ; the number of the vertebrae is 
variable. The sternum is absent in serpents 
and fishes. The ribs are wanting in frogs, 
rays, sharks, and a number of cartilaginous 
fishes. 
It is but a small number of the vertebral 
animals that are without coccyx : these are the 
ternate bats, and the frog kind. Several fishes 
have no neck. The false ribs are always pos- 
terior in quadrupeds. In birds they are both 
before and behind. In the crocodile, and some 
other animals, there are ribs which proceed 
from the sternum, but which do not join the 
vertebrae : others come from the vertebrae, 
and unite anteriorly with the corresponding 
ribs, without any intermediate sternum, as 
in the cameleon. The head is invariably 
placed at the anterior extremity of the verte- 
bral column. It is divided into three parts, 
which, although they differ in relative pro- 
portions, are never wanting. These parts 
are, 1st, The cranium, in which the brain is 
contained, and in the partitions of which the 
cavities of the internal ear, and frequently 
those of the nose, are situated. 2. The face, 
which contains the orbits of the eyes, and the 
nasal cavities, and which terminates inferiorly 
by the upper jaw. 3. The lower jaw, which 
in all animals is moveable, even in the cro- 
codile. The upper jaw is immoveable in 
man, in quadrupeds, and in some reptiles, as 
the tortoise, the crocodile, and others ; it is 
more or less moveable in birds, serpents, and 
fishes. The extremities, when perfect, are 
divided into four parts : those which belong 
to the anterior members are the shoulder, 
the arm, the fore-arm, and the hand; those 
of the posterior are the hip, the thigh, the 
leg, and the foot. These distinctions do not 
obtain among fish, whose extremities are 
merely formed of osseous rays, or bones, 
constituted like a fan, and articulated to parts 
corresponding with tHe shoulder or hip. The 
shoulder is formed ot the scapula placed 
against the back, and the clavicle attached 
to the sternum. The last is wanting in some 
quadrupeds and the cetacea; it is double in 
birds, tortoises, frogs, and many lizards. 
Where extremities exist, the scapula fs al- 
ways found. The arm is constituted by one 
bone; the fore-arm has almost always two; 
even when this last part consists of only one 
bone, there generally appears a kind of se- 
parating furrow. The hand, as it respects 
the number of its bones, considerably varies, 
but the osseous portions of which it consists I 
always form a carpus, metacarpus-, and fing- j 
ers. This is the case even in birds, the 
fingers of which are enveloped in a skin co- j 
vered by feathers. This organization like- 
wise obtains in the cetacea, in which the j 
whole anterior member is reduced to the 
figure of an oar or fin. 
The various parts of the skeleton are usu- \ 
ally disposed with a strict attention to sym- 
metry; so that when divided by a longitudi- 1 
nal section, the two halves are counter-proofs ] 
of each other. In one kind of fish, however, 
called pleuronectes, which comprehends ] 
soles, plaice, turbots, &c. the head is so 
constituted, that the two eyes and the two I 
nostrils are on the same side. 
It may be proper to remark, before we I 
conclude this general account of the skele- 
ton, that although an animal of one class 
may appear similar to that of another, the j 
resemblance is merely outward ; and affects J 
the skeleton, not in the number or arrange- 
nient of its bones, but merely in its total 
proportions. Rats, for instance, appear to 
have wings; but an anatomical examination 
demonstrates these to be in reality hands, j 
the fingers of which are merely somewhat I 
lengthened. In like manner, although dol- I 
phins appear to have fins, composed of an \ 
entire piece, we find under the external 
covering all the bones that compose the an- 
terior extremities of the other mammalia, 
short, and nearly immoveable. 
Of the forms and actions of muscles. 
While the form and number of bones, and 
the mode in which they are articulated, de- 
termine the number, kind, and direction, of ] 
motions they are capable of, the number and 
situation of the muscles determine the num- 
ber, kind, and direction, of the motions that 
are actually performed. 
Muscles are attached to the bones by ten- 
dons. The tendons, like the muscles, are 
composed of fibres, but they are more close 
and firm, and have a silver whiteness. The 
form of the tendon varies as much as that of 
the muscle. Heavy birds, that walk much, 
have the tendons of their limbs ossified at a 
Very early period The same thing takes 
place in the jerboa, and other animals, that 
always leap with their posterior extremities. 
The tendons of the Crustacea and insects 
are frequently articulated with the scaly case 
they have to move, in the same manner as one 
bone is articulated with another; with this 
case they are connected by a membranous li- 
gament. This structure is particularly observ- 
able in the great claws of cray-fish. 
The tendons ot the mollusca are not per- 
ceptible ; but this is in consequence oi the 
tendinous and fleshy parts, both having the 
same colour. The muscles are divided into 
simple and compound . the first compre- 
hend those in which the fibres have one 
direction only;. the most common are the 
ventritorin, the fibres of which are nearly 
parallel, and compose a long bundle of a 
round shape ; their fleshy portions swell in 
